As is well known, in a process of manufacturing glass sheet products to be used for flat panel displays such as a liquid crystal display, a plasma display, and an electroluminescence display, a small-area glass sheet is cut out of a large-area glass sheet, and an edge portion extending along each side of the glass sheet is trimmed off. As a method therefor, a method of cleaving a glass sheet is taken as an example.
As one method of cleaving a glass sheet, there is publicly known a cleaving method that involves cutting as disclosed in JP 07-25633 A. In this method, a scribe is formed in the glass sheet, and then a cutting member is used to press a region on the periphery of the scribe. Thus, a bending moment is applied to the region in the vicinity of the scribe, and a tensile stress generated in the glass sheet due to the bending moment is utilized to propagate a median crack, which is derived from the scribe, in a direction from a scribe surface side of the glass sheet (surface in which the scribe is formed) to another surface side thereof. In this manner, the glass sheet is cleaved.